1. Field of the Invention
The present invention relates to an inspection apparatus for detecting, by an electromagnetic wave, information (physical properties, identity, concentration, presence/absence and the like) of a specimen (object of inspection), and more particularly to an inspection apparatus for detecting the information of the object, utilizing an electromagnetic wave of an arbitrary frequency region of from 30 GHz to 30 THz (referred to herein as terahertz wave).
2. Description of the Related Art
Technical developments utilizing terahertz wave are actively done recently. In particular, the photon energy of the terahertz wave is comparable to the energy of molecular skeletal vibration or intermolecular interaction, and the technology utilizing the terahertz wave is used for analyses of substances for example by a spectrum obtained by a spectroscopic method.
Based on such situation, proposed is a construction for the purpose of detection or analysis of an object of a trace amount, in which a terahertz wave generating unit, a terahertz wave transmission unit, a terahertz wave detection unit and a sensor unit for so disposing an object as to cause an interaction with the terahertz wave are prepared on a same substrate (see Non-patent Document 1).
More specifically, a low-temperature grown gallium arsenide epitaxial layer is transferred for example onto a silicon substrate coated with a dielectric film, and a microstrip line-type transmission line is formed for example by a photolithographic technology. The low-temperature grown gallium arsenide epitaxial layer is provided thereon with two electrodes spaced by a gap of several micrometers to several tens of micrometers, thereby being utilized as a terahertz wave generating unit. A terahertz wave is generated by applying a voltage between the two electrodes and irradiating the gap with an ultra-short pulsed laser beam for example emitted by a mode-locked titanium sapphire laser. The generated terahertz wave is transmitted through the microstrip line type transmission line, and, after an interaction with the object disposed on the transmission line, is detected by a detector of a structure same as that of the terahertz wave generating unit.
In the construction above, the properties, identity, concentration, presence/absence and the like of the object are detected for example by observing the waveform of the terahertz wave transmitting through the microstrip line type transmission line and comparing the change between before and after the object is disposed.
On the other hand, proposed also is a construction, similar to the structure disclosed in Non-patent Document 1 but improved in the detection sensitivity by providing a ringed resonator on the microstrip line type transmission line (see Non-patent Document 2). The construction of Non-patent Document 2 similarly detects the properties, identity, concentration, presence/absence and the like of a substance contained in a liquid object, by determining for example the dielectric constant of the liquid object.
[Non-patent Document 1] Physics in Medicine and Biology, 48(2003), 3625
[Non-patent Document 2] Applied Optics, Vol. 41, No. 10, 2002, pp. 2074